If you are actually taking the truck off the pavement the bigger and heavier engine is a drawback and not an asset. But I would bet that 99% of the Trail Boss trucks never leave the pavement, as with all the Hummers.

2019 was the GM refresh of the Silverado and Sierra 1500 trucks. Not likely to see anything major for several years. GM is also again producing medium duty trucks and that has to take away resources from its light duty trucks.

Want a large gas tank you need to go with Toyota where it is stock or with Ram or Ford where it is an option on their 1500 class pickups. GM does not consider their 1500 trucks to be suitable for towing and so does not bother to provide a large fuel tanks as an option.
When it comes time to replace my Chevy 2500HD pickup it will be most likely with a Toyota Tundra and definitely not a truck from GM.

Gelling is quite common with biodiesel and only starting in 2011 did GM consider it OK to use as they added a heater for the fuel. There may be an aftermarket additive and if I lived where biodiesel was the only option I would be looking for it.

It boggles my mind that anyone would pay the money and take the time to make a truck less able to function on and off the road just because they think it looks cool and will be a chick magnet - if only it was that easy. There seems to be a correlation with the higher the truck height the lower the IQ of its owner. But then again, IQ may be greatly overrated when a complete idiot is in power in the White House.

Changing based on mileage is simple but it is also the worst way to go. The simple reason why is that engine oil life is a function of engine hours and not auto miles. Compare two identical vehicles and one that is driven in stop and go situations and averages 30 mph over 5,000 miles. The oil has been in use for 167 hours. The second vehicle has been used mostly on the highway at an average speed of 60 mph and so in 5000 miles the engine oil as been in use for 83 hours. Would you expect the oil to be in the same condition with both vehicles?
My diesel truck has an engine hours reading and that is what I use to change the oil. This is also a trend in the trucking industry as they are switching over from miles driven to hours of use. The more often they change the oil the more it costs them with the truck out of service and this is there primary concern.
The DIC should in theory be evaluating the type of use and hours of use and aspects like cold driving with short trips that add to soot buildup, but I use it as a guide only.

My current truck has the GM drop-in bedliner and a spray in one would have been a better way to go. The bedliner cost me nothing as the dealer really wanted to move the truck. I would have an aftermarket guy do the spray-in lining and get a better job for the same price as the factory charges.
A friend bought a commercial kit and made the cost back with the first two trucks he treated for the local dealer. Figure on about $30 worth of product with a $350 bedliner coating job.

GM makes more money on the financing than on the sale of many of its vehicles. MSRP is not where I start but rather the dealer invoice. Even dealer invoice is a fiction as it does not reflect the actual price the dealer pays the factory as it excludes the rebated amounts which are based on sales volume. This is why a higher volume dealer can afford to sell a truck at a lower price and still come out ahead.

Go to the dealer's lot and see what is on the trucks that they have in inventory. Not unusual for the factory to use more than one company's tires, probably to get a lower price.
Regardless they will be all-terrain and not what I would want for snow or off-road use where one is better off using All-Terrain tires. I always remove the factory tires and sell them on craigslist and buy what I want at a local tire store.

I care about the turning radius and so want as short a wheelbase as possible. That translates into a double cab with the standard length bed (6.5 feet). I would only but a trim that provided this configuration. It is why I ended up buying a 2500HD Duramax in 2011 instead of the 3500HD where this was not offered by the factory.
With a short bed the truck would be no better than my full size SUV for carrying cargo.

The Octane rating is as was mentioned a measure of pre-ignition or knock resistance and it is not a linear rating. If you take 10 gallons of 89 octane rated gasoline and mix it with 2 gallons of 100 octane fuel the result is going to be in the 93 octane range. People assume that if you mix 5 gallons of 93 octane and 5 gallons of 100 octane gas the result is a 96 octane fuel and it does not work that way with respect to pre-ignition.
With my coupe that was designed for premium my mpg would drop by about 7% if I used 89 octane gas in the tank. The 93 octane gas costs about 10% more so there is no gain either way. So I used premium fuel in the coupe.
On the other hand my 2018 Traverse has a V-6 engine designed to run on 87 octane gasoline and going with higher octane gas would be a complete waste of money in every respect. Every 50,000 miles I do plan to invest in fuel injector cleaner and add it to the tank and that is a worthwhile investment.

I only replace a vehicle when it is no longer needed or useful or safe or reliable. Plan to sell my 2011 heavy duty diesel pickup this year and buy a gas powered 1/2 ton as I am no longer doing heavy towing or hauling. Every truck I have owned has been replaced at around 170,000 miles but it was to get a better engine, airbags, more towing capacity, and all those trucks were at least 10 years old.
With lead free gas an engine is good for 300,000 miles. There may be problems with a head gasket or fuel pump or water pump or alternator or air conditioning but those are relatively cheap repairs as compared to buying a new truck. My next gas powered 1/2 ton is going to cost me over $40,000 and the state sales tax and DMV fees will be over $5,000. I can do a lot of repairs for $5,000.
Reliability is a concern and I would be most concerned with a work truck that affected my income when it was in the shop or if it might break down thousands of miles from my house. I have had breakdowns and there was the cost to get the parts expedited to the town and the cost for a hotel and restaurant meals until I could get back on the road. With an RV in tow or a boat trailer it would be even more of a problem and so I pay more to have vehicles that hopefully I can rely on. That has not been the case with my Duramax diesel that has had numerous emissions controls problems that have stopped it in its tracks and caused us to cut short three vacation trips. I now only use it in the local area and close to home.

When I am on backcountry roads or running trails my mpg drops and the availability of gas stations is limited. With my 2011 diesel truck I was initially spending more time locating gas stations that sold diesel than planning overnight stops on my travels. It has gotten better but I am still glad that it has a 36 gallon fuel tank. MPG with a 2019 Silverado 1500 with the 6.2L would be no better in these situations than my diesel 2500HD truck.
In the mountains or on twisty roads or on dirt roads the 18-20 mpg highway drops to 14-15 mpg and so my range is 34 x 14 or 476 miles. With the 1500 pickup my range would be 24 x 14 or 336 miles and a difference of 140 miles is significant, and the reason why I will most likely be replacing the 2500HD with a 2020 Toyota Tundra or a Ram 1500. I am not about to go back to carrying fuel cans on the roof rack.

Speed is the killer. Air resistance goes up with the square of speed so there is four times as much energy needed to push the truck through the air at 60 mph as at 30 mph. With any new vehicle I spend time finding the sweet spot where MPG is the highest and the speed at which the vehicle's mpg will start to plummet.
For my 2018 Traverse at 60 MPH on the highway I average 30+ MPG. At 72 mph (10% over speed limit) it gets about 24 mpg. With my diesel 2500HD pickup at 60 MPH it gets 18-20 mpg but at 72 mph it drops to 16-17 mpg.
Tires are important and the more aggressive the tread and the larger/heavier the tire the worse the fuel economy will be for any vehicle.
Ethanol is a great scam by Archer Midland Daniels and the other corn industry companies that improves their profits but does so at the expense of motorists. A gallon of ethanol has a Btu or 76,000 per gallon as compared to gasoline at 115,000 Btu per gallon. With a third less energy adding ethanol to gasoline will greatly reduce fuel economy for any vehicle.
A new truck with a larger cab and greater payload and greater towing capacity is not going to come without some costs. Drivetrain gearing is also all over the board with today's trucks. For Chevy 1500 trucks with the 6.2L engine the standard gears are 3.23 but with the tow package the standard gears are 3.42, and that alone could account for a 1 mpg difference in miles per gallon.